1. Field
This disclosure relates generally to communication, and more specifically to techniques for scaling the sampling rate of an analog-to-digital converter.
2. Background
Wireless communication systems are widely deployed to provide various communication services such as broadcast, voice, video, packet data, messaging, etc. These wireless systems include broadcast systems, cellular systems, etc. A wireless system may operate in an environment where jammers may be present. Jammers are large amplitude undesired signals. The jammers may correspond to strong narrowband frequency components (e.g., for color carrier, sound carrier, etc.) from an interfering source or intermodulation distortion generated by a receiver. The jammers may cause various deleterious effects such as failure to detect and acquire a signal from a desired system, degradation in decoding performance, etc.
Analog filters are often used in a receiver to pass the desired signal while suppressing out-of-band jammers that couple to the antenna. Any residual jammer energy remaining prior to an analog-to-digital conversion can potentially alias into the signal band. This may cause a degradation in receiver sensitivity, bit rate error, and/or other types of signal degradation.
Analog-to-digital (ADC) and other digital logic clocked at the ADC sampling rate may also degrade receiver performance For example, a sample clock may have a harmonic falling inside the RF signal bandwidth of one of the active receivers in a user device. Digital signals in the sample clock domain may couple to sensitive low noise amplifier (LNA) and/or mixer circuits, where a harmonic component creates an in-band jammer.
Another common problem is that the sampling clock, or other digital signals in the sample clock domain may couple into the receiver synthesizer, thereby modulating the VCO control voltage. As a result, spurious components may be presented in the VCO output. These spurious components may create continuous wave (CW) jammers at the receiver output and/or other broadband interference resembling jammer aliasing.
There is a need in the art for improved techniques for avoiding jammer aliasing and other similar interference.